Minimally invasive surgery (“MIS”) is quickly becoming standard for the implantation of prosthetic components into a patient. For example, the use of an MIS shoulder replacement technique involves a skin incision of approximately 7-9 cm and is performed without the previously required laying-open of the patient's entire shoulder area. MIS techniques for joint replacement may reduce trauma to the patient, with less pain, less blood loss, shorter convalescence, faster stabilization, and fewer post-operative restrictions on exercising of the joint. The use of MIS may also give the prosthetic joint a better fixation and function than traditional surgery, which in turn can contribute to an increased lifetime for the prosthetic joint. MIS also can be done with considerably shorter hospitalization time than traditional techniques, and may even be available for outpatient procedures, providing an economic benefit linked to positive patient outcome in many cases.
In a prosthetic shoulder joint replacement, whether accomplished via MIS or any other suitable surgical technique, the humeral head is removed and replaced with a prosthetic head which is fixed to the bone using a stem within the humeral metaphysis and/or diaphysis shaft. The humeral head articulates with the native glenoid (hemiarthroplasty) or with a prosthetic glenoid component. The humeral osteotomy is made at or near the anatomic neck of the humerus. This osteotomy defines a humeral head neck shaft angle and version of the final implant. In patients with deformity associated with arthritis, the anatomic neck is difficult to define, making it difficult for the surgeon to determine to precise location of this osteotomy. Standard generic stock cutting guides currently used for this procedure still require the surgeon to identify these anatomic landmarks to place the cutting guides.
One factor which may lead to success for a total shoulder replacement technique is the provision of a clear overall view of the wound during the operation in order to achieve precise surgery and the desired positioning for the prosthetic components. In the precise surgery associated with the implantation of a shoulder replacement prosthetic component, it is important for the head of the humerus to be removed with great precision. For this purpose an osteotomy template is generally used, whereby the level and orientation of the planned cutting plane is transferred to the patient's humerus to guide the surgeon. With the preoperative planning procedures that are currently under development, a computer model of the patient's humerus will often be produced, based on CT, radiographic, or other preoperatively obtained images. Based on this model, a desired cutting plane for the patient's humerus can be determined.
Osteotomy templates exist for use in conventional surgery, but there is currently a need for improved osteotomy templates. A resection guide for use in many hip, shoulder, or other types of prosthetic replacements, whether using MIS or another surgical style, would be useful than currently used guides by being considerably smaller, intended for insertion through different openings, employing different anatomical landmarks, allowing for a more accurate osteotomy, and easier to position in the planned position than the currently used resection guides.
Since traditional osteotomy templates are not adapted to the individual patient, they require the surgeon to remove pathologic bone to identify landmarks in order to place the template and make a cut or to use the anatomic landmarks to make an osteotomy without any template or cutting guide. The difficulty lies in the surgeon's ability to identify anatomic landmarks in the pathologic condition. This means that for patients with anatomical deviations, there is a reduction in precision with traditional multi-use osteotomy templates, thereby giving a final result that is not optimal. For patients with greater anatomical deviations, moreover, the majority of multi-use templates will be difficult to use on account of limitations in the possibilities for adjustment. Even for patients without great deviations, when using multi-use templates it will be necessary to carry out adjustments of the osteotomy template during the operation, resulting in an increased risk of error, increased operating time and thereby an increased risk of complications.